1. Field of the Invention
This invention relates to an image projection method and an image projector using a laser beam.
2. Related Background Art
Image projectors are known as image display apparatuses adapted to display a large image.
A projector has a projection tube as light source for projecting beams of light onto a display screen so as to throw an image on the display screen and the viewers see the image displayed on the display screen.
Hitherto, a highly bright projection tube is used as light source for a projector. Then, an image is displayed on a display screen which may typically be a liquid crystal panel as beams of light are projected from the projection tube.
However, known projection tubes are not satisfactory in terms of brightness and color reproducibility and hence projector systems using lasers of red, blue and green as light source have been proposed from the viewpoint of easy modulation of video signals, improved color reproducibility and enhanced brightness.
On the other hand, projector systems using laser beams face a problem of security.
For instance, laser beams can accidentally strike the eyes of viewers in the case of projector systems using laser beams and designed for home use. Laser beams are highly dangerous if they directly strike human eyes. Therefore, such a risk provides a serious problem for commercializing projector systems using laser beams regardless of the intensity of the laser beams emitted from the projector system.
In view of the above problem, it is therefore the object of the present invention to provide an image projection method and an image projector that can ensure an enhanced level of security and are adapted to instantaneously shut down the laser beams emitted therefrom when an obstacle intersects any of the optical paths of the laser beams.
According to the invention, the above object is achieved by providing an image projection method for projecting laser beams onto a display screen to display an image, wherein a detection wave is projected onto the display screen along with the laser beams, and the detection wave reflected by the display screen is detected so as to find out an obstacle intruding into the projection area of the laser beams.
According to the invention, there is also provided an image projector comprising:
a laser beam source for projecting laser beams to display an image;
a detection wave source for projecting a detection wave;
a display screen to which the laser beams and detection wave are projected;
a reflected wave detection means for detecting the detection wave reflected by the display screen so as to find out an obstacle intruding into the projection area of the laser beams; and
a laser beam shutdown mechanism for shutting down the laser beams according to the detection signal output from the reflected wave detection means.
Preferably, in the image projection method and the image projector according to the invention as defined above, the detection wave is used for detecting an obstacle.
More specifically, a detection wave is projected onto the display screen simultaneously with the laser beams for displaying an image projected onto the display screen and the detection wave reflected by the display screen is monitored. As an obstacle intrudes into the projection area of the laser beams, the detection wave is intercepted by the obstacle to give rise to a change in the intensity of the detected reflection wave. Therefore, the risk of exposing a viewer to the laser beams for a prolonged period of time can be successfully avoided by shutting down the laser beams instantaneously according to the result of the detecting operation.
The detection wave for monitoring the operation of the projector is not visually sensed by viewers so that the image displayed on the display screen is not affected by the detection wave.
In another aspect of the invention, there is also provided an image projection method for projecting laser beams onto a display screen to display an image, wherein the image displayed on the display screen is picked up, and the difference between the image to be displayed and the displayed image is detected so as to find out an obstacle intruding into the projection area of the laser beams.
According to the invention, there is also provided an image projector comprising:
a laser beam source for projecting laser beams to display an image;
a display screen to which the laser beams are projected;
an image pickup means for picking up the image displayed on the display screen;
an image processing means for detecting the difference between the image to be displayed and the displayed image so as to find out an obstacle intruding into the projection area of the laser beams; and
a laser beam shutdown mechanism for shutting down the laser beams according to the detection signal output from the image processing means.
Thus, as an image is projected onto the display screenby laserbeams, the image displayed on the display screen is monitored. If an obstacle intrudes into the projection area of the laser beams, the laser beams projecting the image is intercepted by the obstacle to give rise to a difference between the image to be displayed and the displayed image. Therefore, the risk of exposing a viewer to the laser beams for a prolonged period of time can be successfully avoided by shutting down the laser beams instantaneously according to the result of the detecting operation.
In still another aspect of the invention, there is provided an image projection method for projecting laser beams onto a display screen to display an image, wherein the laser beams are projected also onto a detection area of the display screen located outside the displayed image, and the laser beams reflected by the detection area of the display screen are detected so as to find out an obstacle intruding into the projection area of the laser beams.
According to the invention, there is also provided an image projector comprising:
a laser beam source for projecting laser beams to display an image and also projecting laser beams onto a detection area located outside the displayed image;
a display screen to which the laser beams are projected;
a reflected beam detection means for detecting the laser beams reflected by the detection area of the display screen so as to find out an obstacle intruding into the projection area of the laser beams; and
a laser beam shutdown mechanism for shutting down the laser beams according to the detection signal output from the reflected beam detection means.
Preferably, in the image projection method and the image projector according to the invention as defined above, the detection wave is used for detecting an obstacle.
More specifically, a laser beam for displaying an image and detecting an obstacle is projected onto the display screen and the reflected laser beam is monitored. As an obstacle intrudes into the projection area of the laser beams, the laser beams are intercepted by the obstacle to give rise to a change in the intensity of the detected reflection wave. Therefore, the risk of exposing a viewer to the laser beams for a prolonged period of time can be successfully avoided by shutting down the laser beams instantaneously according to the result of the detecting operation.
As described above, according to the invention, it is now possible to shut down the laser beams projected form a laser beam source onto a screen instantaneously when an obstacle intrudes into the projection area of the laser beams so that the present invention can provide an image projection method and an image projector that are highly safe in operation.
Additionally, if a detection wave is used for detecting an obstacle intruding into the projection area, it is not visually recognized by viewers nor affect the image projected onto the display screen. Furthermore, the detection wave is not dangerous at all.
If a laser beam is used for detecting an obstacle intruding into the projection area, the laser beam is shut down instantaneously even though it irradiates a viewer so that it does not do any harm to the viewer. Additionally, this arrangement does not require the use of a detection wave source.